Abstract
Splenic diffuse red pulp small B-cell lymphoma (SDRPL) is a rare disease, representing <1% of all non-Hodgkin lymphomas (NHL). The most common clinical manifestations include splenomegaly, lymphocytosis, and hemocytopenia. A diagnosis of SDRPL can be challenging, as it shares multiple clinical and laboratory features with splenic marginal zone lymphoma (SMZL), hairy cell leukemia (HCL), and HCL variant (HCL-v). Obtaining splenic tissue remains the gold standard for diagnosis. In the cases where splenic tissue is not available, diagnosis can be established by a review of peripheral blood and bone marrow studies. SDRPL is characterized by a diffuse involvement of the splenic red pulp by monomorphous small-to-medium sized mature B lymphocytes effacing the white pulp. The characteristic immunophenotype is positive for CD20, DBA.44 (20 to 90%), and IgG, and typically negative for CD5, CD10, CD23, cyclin D1, CD43, annexin A1, CD11c, CD25, CD123, and CD138. The Ki-67 proliferative index is characteristically low. Cyclin D3 is expressed in the majority of SDRPL in contrast with other types of small B-cell lymphomas, thus facilitating the recognition of this disease. There is no standard treatment regimen for SDRPL. Initial treatment options include splenectomy, rituximab monotherapy, or a combination of both. Chemoimmunotherapy should be considered in patients with advanced disease at baseline or progression.